Evans Tempcon Heater Control Valve

Evans Tempcon Heater Control Valve
for systems equipped with the EVANS electric coolant valve and control
This guide is intended for use with the EVANS electronic
coolant valve shown at left and its control system.
For other electronic coolant control systems, refer to
Cable-less Electronic Valve – 2002 and Prior.
For other HVAC system components, diagnoses, and
repair, refer back to the Cable and Rotary Control
Systems Menu for the appropriate topic.
Read the entire troubleshooting guide and familiarize yourself with the
procedures before attempting any of the procedures described in this document.
There are two types of actuators on the valves that Evans supplies as shown in the
illustration below. The significant difference in the valves is the arrangement of the
terminals in the connector housing on the actuator. Old style valves used from 2002 to
2005 have a distinct “T” pattern as shown on the right and the manufacturer’s logo
“Seitz” on the actuator, while newer valves used from 2006 and later have the terminals
located in the four corner positions of the connector housing, as seen on the left, and
the actuator manufacturer’s logo “CEI” on the cover.
Inspect the main harness valve connector and valve pin pattern to ensure the correct
valve was previously installed on the vehicle. The connector pattern should have three
wires in a straight line for the old style valve (on left below), not a 3 corner or ‘L’ pattern
for the new valve (on right below). If a new style valve has been installed on a vehicle
with an older style harness, a jumper needs to be installed between the harness and the
valve to correctly orient the terminals for the new style valve. Contact your service parts
representative if it is determined a jumper is required and you do not have one.
Evans service parts kit # RV218999 is intended for use to replace an old style
valve with a new valve and contains the necessary jumper along with the valve.
Service parts kit # RV218967 is intended for systems that have the new style
valve and harness and does not contain the jumper harness for older systems.
When plugging the connector from the
harness into the valve connector
socket, be sure to push the connector straight into the socket and do
not rock the connector as it is inserted as this could cause the pins in
the connector to become bent or misaligned.
Before attempting to troubleshoot, verify that the HVAC system (other than temperature
control) is operating correctly. With the vehicle running, test-operate the system and
check the following:
Blower Motor and 4 operating speeds
Mode selector switch and air distribution system
A/C system (engine-driven compressor, refrigeration system, etc.).
With the vehicle running and the A/C system engaged (Blower turned on, Mode
selector set to "MAX A/C", Temperature dial rotated to full cool), clamp off the
heater inlet hose to see if the A/C system is cooling properly. Test the A/C
performance using the A/C Systems Operational Check and Estimated A/C
Performance Guidelines. Once this has been determined (and corrected if
necessary), remove the clamp from the coolant inlet hose.
If a significant loss in cooling capacity in the A/C system occurs when the clamp
is removed, shut the vehicle off, and carefully follow the step-by-step directions
listed below for troubleshooting the coolant control system. If a problem is found,
repair/correct the fault before proceeding to the next step. When troubleshooting
electric and/or electronic components, care must be taken to prevent component
damage while inspecting, using a test meter, light, etc. If questions or concerns
arise during the troubleshooting process, contact Evans Tempcon for telephone
assistance before proceeding further (1-800-878-7147).
The temperature control is located in the center of the HVAC system control
panel. Rotate the potentiometer knob to verify smooth operation. The knob
should rotate freely from the cool stop (blue), to the warm stop (red). Do not
force the knob to rotate past the cool or warm stops. Doing so will cause
irreparable damage to the potentiometer control. If the knob can be rotated past
the internal stop at the full cool and full heat positions, the potentiometer must be
replaced before any further valve diagnostics is done.
Locate the electronic coolant valve assembly in the heater base unit
compartment, near the Evans Heater-Evaporator unit (on the firewall).
electrical connector is located on the top of the actuator housing.
Verify that the port on the outlet side of the valve is connected to the inlet tube on
the heater coil. A flow direction indicator is located on the side of the valve to
help distinguish inlet and outlet ports. Also, the inlet side of the valve is always
on the same side as the harness connector. New valves also have tape wrapped
around the inlet port that clearly identifies the inlet port (see the illustration at the
beginning of this guide). The coolant supply hose from the engine connects to
the inlet side of the valve.
NOTE: The electronic coolant valve is a "directional" valve, and must be
correctly installed, or it will not function properly. Coolant valves
installed with the coolant flow reversed will leak coolant past the valve
cylinder resulting in poor A/C performance. Valves that have been installed
backwards should be replaced as damage to the seals can occur if the
coolant flow has been applied in the wrong direction.
Removal of the coolant valve should be performed when the engine is cold.
Attempting to remove the valve from the system when the engine is hot could
result in burns and/or serious injury due to extremely hot coolant escaping under
pressure. Do not start the engine while the coolant lines are disconnected as the
engine will quickly pump the system dry, which could result in damage to the
Verify that the heater supply hose (containing the coolant valve) is actually the
hose coming from the supply port on the engine. The supply port is usually on,
or near the engine thermostat housing. To positively identify the supply line,
remove the valve from the coolant lines and place both ends of the lines into a
container to capture escaping fluid. Have an assistant "turn over" the engine
while you observe the coolant lines. The line that discharges coolant when
the engine is turned over is the supply line for the HVAC system.
NOTE: Note this procedure will not be useful for systems with a bypass or “H”
fitting. Correct plumbing well have to be checked at “H” fitting in this case.
See your vehicle chassis manual for systems with “H” bypass fittings in the
coolant lines.
Verify positive electrical connections at the coolant valve. Verify that a new valve
has not been installed on an older system without a jumper harness.
a. If a new valve has been installed on an older system a jumper harness is
required between the main harness and valve.
b. If a new valve is installed on newer system, a jumper harness should not
be used between the valve and main harness.
Unplug the wire harness connector from the coolant valve connector. Check the
socket terminals for damage. Inspect the pin terminals on the coolant valve
connector for damage. If any pins in the valve connector are loose or broken,
replace the valve. Refer to the Electrical System Schematics for correct pin
locations and wire colors.
Note: Some early production Seitz valve actuators have a short four wire lead. Check
the leads to insure they match the pin locations on the wire harness connector.
The blue wire on the valve lead is for the manufacturer’s testing purposes and is
not used during normal valve operation. When replacing this valve, order
Evans kit # RV218999.
Use a DC voltage test meter and find a good vehicle ground for the negative
probe. Do not use the negative connection on the wire harness.
Insert the positive probe from the meter into the black wire terminal on the wire
harness valve connector. The voltage value should always read 0 VDC because
this is the ground connection for the hot water valve.
NOTE: If voltage is detected on this circuit the entire harness should be visually
inspected for damage, incomplete or misaligned connections. Do not proceed
with testing until this voltage bleed has been resolved.
Insert the positive probe from the meter into the red wire terminal of the wire
harness valve connector. The voltage value should always read near the
vehicle’s regulated voltage. If not then you have an issue with the wire harness or
NOTE: Low system voltage could be the result of numerous causes and will cause
the valve to fail to operate. Do not proceed with testing until this voltage issue
has been resolved.
Insert the positive probe from the meter into the yellow wire terminal of the wire
harness valve connector. Rotate the temperature control knob to the far left
(BLUE) position. The voltage value should always read near the vehicle’s
regulated voltage when the potentiometer is in the closed (BLUE) position.
Rotate the temperature control knob to the far right and measure the yellow wire
The voltage value should always read 0 VDC when the
potentiometer is in the open (RED) position.
If the proper voltage readings are not measured at either valve position and all
other electrical issues have been resolved, then replace the temperature control
potentiometer (Evans replacement part # RV218549).
If the voltages readings at the valve connector are normal then carefully plug the
connector into the valve and then remove the HVAC control panel to access the
temperature control potentiometer connector.
Remove the connector from the potentiometer and install a jumper wire on the
connector from the red wire terminal to the yellow wire terminal. This will apply
full vehicle voltage to the valve and force the valve to fully close. Look into the
valve coolant inlet to visually verify that the valve is completely closed.
Change the jumper from the red wire terminal to the black wire terminal so that
the jumper connects the yellow wire terminal to the black wire terminal. This will
ground the control wire of the actuator and the valve should be completely open.
Visually verify again.
NOTE: By nature of the design of the valve, when the coolant valve gate is fully
open, half of the valve port opening appears to be blocked. At no time will the valve
port appear to be empty.
If the valve does not visually open or close completely then replace it, attach the
coolant inlet hose and secure assembly for proper operation.
Proceed to SYSTEM VERIFICATION TEST to determine if repair is complete.
Keep in mind that if heated coolant has traveled through the heater core prior to
these tests then it will take several minutes before the core cools and proper
valve operation can be verified. Operating the A/C system for a few minutes will
speed up the process of cooling the heater core.
Attach both coolant hoses to the correct valve ports, reinstall the control panel,
and secure the vehicle for operation.
Set the Mode Switch (right side of control panel) to “Vent”.
Rotate the temperature control to full cool (BLUE - far left position).
Start the engine and set the engine speed to1500 rpms if possible. Remember
to have the vehicle transmission in neutral gear and the parking brake ON.
Measure the Fresh Air inlet temperature and the dash vent air temperature
nearest to the unit (passenger side dash louver) and record the values. Repeat
these measurements at 5 minute increments until the engine has reached normal
operating temperatures.
If the inlet and outlet temperature difference does not vary significantly as the
engine warms the coolant then the valve can be considered completely closed. If
the temperature difference increases significantly then the valve is leaking
coolant through the heater core; replace the valve assembly.
Rotate the temperature control to full heat; an immediate significant temperature
change should occur between the inlet and outlet temperature readings.
Rotate the temperature control back to full cool and monitor the temperature
differential. The change will be slower, but the outlet temperature should drop to
where no significant difference is detected between inlet and outlet temperatures.
If the temperature difference does not stabilize then the valve is leaking coolant
through the heater core; replace the valve assembly.
Once the faulty component has been identified, the new replacement
permanently installed, and everything is buttoned back up, perform an actual
function test for warm and cool air with the vehicle running. Test A/C
performance using the A/C Systems Operational Check and Estimated A/C
Performance Guidelines.
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